Influence of Hybrid Coconut Husk Ash/Periwinkle Shell Ash and Silicon Carbide Reinforcement on Microstructure, Hardness and Wear Properties of Al–Zn Based Matrix Composites

Abstract

Aluminum is widely used as a structural material in the automotive and aerospace sectors because of its low density and ease of processing. However, its relatively low melting temperature and limited strength restrict its performance in demanding applications. To address these limitations, ceramic reinforcements such as silicon carbide and alumina are commonly introduced due to their effectiveness and affordability. In recent years, attention has shifted toward low-cost and environmentally sustainable alternatives, particularly agro-waste–derived materials. Despite growing interest in such reinforcements, there is limited information on the combined use of Coconut Husk Ash (CHA), Periwinkle Shell Ash (PSA), and Silicon Carbide (SiC) as hybrid reinforcements in Al–Zn alloys. This study therefore examines the microstructural characteristics using Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM-EDS), hardness, ultimate tensile strength, and wear performance of Al–Zn alloy composites reinforced with varying proportions of CHA, PSA, and a constant 2 wt% SiC. The micrograph of the unreinforced alloy revealed a predominantly single-phase structure with zinc-rich dendritic features, along with noticeable voids likely associated with the absence of reinforcement. In contrast, the hybrid composites exhibited a more uniform distribution of reinforcement particles within the aluminum matrix. Elemental analysis confirmed the presence of constituents such as calcium, manganese, magnesium, silicon, iron, and carbon, which are associated with the added reinforcements and are believed to enhance the observed properties. The reinforced composites consistently demonstrated higher hardness and tensile strength compared to the base alloy, with values increasing as the reinforcement content increased. Similarly, wear resistance improved with increasing reinforcement content, with the best performance recorded for Sample E and at Sample F there is a decline in mechanical properties which might be linked to particle agglomeration, poor interfacial bonding and reduced matrix continuity. Overall, the findings indicate that hybrid reinforcement using CHA, PSA, and SiC significantly enhances the mechanical and tribological performance of Al–Zn alloys. This approach not only improves material properties but also offers an effective means of utilizing agricultural waste, thereby providing both economic and environmental benefits.